Method of making flexible semiconductor device with graphene tape

ABSTRACT

A flexible semiconductor device includes a first tape having bonding pads and conductive traces formed. A semiconductor die having a bottom surface is attached to the first tape and electrically connected to the bond pads by way of electrical contacts. A second tape is attached to a top surface of the semiconductor die. The first and second tapes encapsulate the semiconductor die, the electrical contacts, and at least a part of the conductive traces.

This application is a divisional application of a U.S. patentapplication entitled “FLEXIBLE SEMICONDUCTOR DEVICE WITH GRAPHENE TAPE”,having a serial number of Ser. No. 15/365,549, having a filing date ofNov. 30, 2016, having common inventors, and having a common assignee,all of which is incorporated by reference in its entirety.

BACKGROUND

The present invention relates to semiconductor device assembly and, moreparticularly, to a flexible semiconductor device assembled with agraphene tape.

With the expansion of the wearable device market, the demand for lowcost, flexible semiconductor packages has gotten stronger. Conventionalsemiconductor packages assembled with encapsulant materials like plasticor ceramic are very rigid, which results in low flexibility and thusthey are not ideal for wearable devices.

It would be advantageous to have a method and materials for assemblinglow cost, flexible devices.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with objects and advantages thereof, may best beunderstood by reference to the following description of preferredembodiments together with the accompanying drawings in which:

FIGS. 1-5 are cross-sectional side views of various flexiblesemiconductor devices in accordance with embodiments of the presentinvention;

FIG. 6 is a top plan view of a second tape of the semiconductor deviceof FIG. 5 in accordance with an embodiment of the present invention;

FIG. 7 is a top plan view of a graphene tape of the semiconductordevices of FIGS. 1-5 in accordance with an embodiment of the presentinvention;

FIGS. 8-10 are top plan views of a flexible semiconductor device inaccordance with embodiments of the present invention;

FIGS. 11-13, 14A, 14B, 15A, 15B, 16A, 16B, and 17 are a series ofdiagrams illustrating steps in assembling a flexible semiconductordevice in accordance with an embodiment of the present invention; and

FIGS. 18-20 are a series of diagrams illustrating steps in assembling aflexible semiconductor device in accordance with another embodiment ofthe present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The detailed description set forth below in connection with the appendeddrawings is intended as a description of presently preferred embodimentsof the invention, and is not intended to represent the only forms inwhich the present invention may be practised. It is to be understoodthat the same or equivalent functions may be accomplished by differentembodiments that are intended to be encompassed within the spirit andscope of the invention. In the drawings, like numerals are used toindicate like elements throughout. Furthermore, terms “comprises,”“comprising,” or any other variation thereof, are intended to cover anon-exclusive inclusion, such that module, circuit, device components,structures and method steps that comprises a list of elements or stepsdoes not include only those elements but may include other elements orsteps not expressly listed or inherent to such module, circuit, devicecomponents or steps. An element or step proceeded by “comprises . . . a”does not, without more constraints, preclude the existence of additionalidentical elements or steps that comprises the element or step.

In one embodiment, the present invention provides a semiconductor deviceincluding a first tape that has a plurality of bonding pads and aplurality of conductive traces formed thereon, wherein the plurality ofbonding pads are formed in a first center area of the first tape, andthe plurality of conductive traces are formed in the first center areaand extend from the plurality of bonding pads to a first peripheral areasurrounding the first center area. The semiconductor device furtherincludes a first semiconductor die attached to the first tape andelectrically connected to the plurality of bond pads by way of aplurality of electrical contacts, and a second tape having a secondcenter area attached to the first semiconductor die, and a secondperipheral area surrounding the second center area attached to the firstperipheral area of the first tape, wherein the first and second tapeencapsulate the first semiconductor die, the plurality of electricalcontacts, and at least a part of the plurality of conductive traces.

In a further embodiment, the present invention provides a method forassembling a semiconductor device. The method includes providing a firsttape that has a plurality of bonding pads and a plurality of conductivetraces formed thereon, wherein the plurality of bonding pads are formedin a first center area of the first tape, and the plurality ofconductive traces are formed in the first center area and extend fromthe plurality of bonding pads to a first peripheral area surrounding thefirst center area. The method further includes attaching at least afirst semiconductor die to the first tape and electrically connected tothe plurality of bond pads by way of a plurality of electrical contacts,and attaching a second center area of a second tape to the firstsemiconductor die and a second peripheral area surrounding the secondcenter area to the first peripheral area of the first tape, wherein thefirst and second tape encapsulate the first semiconductor die, theplurality of electrical contacts, and at least a part of the pluralityof conductive traces.

Referring now to FIG. 1, a cross-sectional side view of a semiconductordevice 100 in accordance with a first embodiment of the presentinvention is shown. The semiconductor device 100 includes a first tape102 having a plurality of bonding pads 104 and a plurality of conductivetraces 106 formed thereon. The plurality of bonding pads 104 are formedin a first center area 108 of the first tape 102, and the plurality ofconductive traces 106 are formed in the first center area 108 and extendfrom the plurality of bonding pads 104 to a first peripheral area 110that surrounds the first center area 108. In a preferred embodiment, theplurality of conductive traces 106 and the plurality of bonding pads 104comprises graphene.

The semiconductor device 100 further includes a first semiconductor die112 having a bottom surface attached to the first tape 102 andelectrically connected to the plurality of bond pads 104 by way of aplurality of electrical contacts 114, and a second tape 116 having asecond center area 118 attached to a top surface of the firstsemiconductor die 112, and a second peripheral area 120, that surroundsthe second center area 118, attached to the first peripheral area 110 ofthe first tape 102. The plurality of electrical contacts 114 are solderballs or solder bumps, that are attached to the bottom surface of thefirst semiconductor die 112 by controlled collapse chip connection (C4)process. The first and second tapes 102 and 116 encapsulate the firstsemiconductor die 112, the plurality of electrical contacts 114, and atleast a part of the plurality of conductive traces 106. In a preferredembodiment, a vacuum is applied between the first and second tapes 102and 116 to draw the first and second tapes 102 and 116 together. Theplurality of electrical contacts 114 are attached to the plurality ofbonding pads 104 by air pressure. In a preferred embodiment, the firstand second peripheral areas 110 and 120 are attached to each other byway of adhesive materials disposed therebetween. In another preferredembodiment, the first and second peripheral areas 110 and 120 are heatedand attached to each other. In a preferred embodiment, at least one ofthe plurality of conductive traces 106 has a portion 122 exposed fromthe second tape 120 such that the exposed portion 122 of the at leastone of the plurality of conductive traces 106 acts as an input andoutput terminal of the semiconductor device 100.

FIG. 2 shows a cross-sectional side view of a semiconductor device 200in accordance with a second embodiment of the present invention. Thesecond embodiment is similar to the first embodiment described above,except that the semiconductor device 200 further includes a metal plate202 disposed between the first semiconductor die 112 and the second tape116 that protects the first semiconductor die 112 from being bent, and ahorizontally non-conductive layer 204 disposed between the first tape102 and the first semiconductor die 112 that locks the plurality ofelectrical contacts 114 in place to prevent shifting between theplurality of electrical contacts 114 and the plurality of bonding pads104. In a preferred embodiment, the horizontally non-conductive layer204 has a thickness ranging from 10 m to 50 m. The horizontallynonconductive layer 204 preferably comprises adhesive material such asanisotropic conductive film or B-stage epoxy. In a preferred embodiment,the horizontally non-conductive layer 204 comprises a plurality ofopenings 206 corresponding to the plurality of bond pads 104, whereinthe plurality of electrical contacts 114 are physically and electricallyconnected to the plurality of bond pads 104 through the plurality ofopenings 206.

FIG. 3 shows a cross-sectional side view of a semiconductor device 300in accordance with a third embodiment of the present invention. Thethird embodiment is similar to the second embodiment described above,except that the horizontally non-conductive layer 204 at least partiallycontacts the bottom surface of the first semiconductor die 112 due tothe vacuum applied between the first and second tapes 102 and 116. Inanother preferred embodiment, the horizontally nonconductive layer 204fills the gap between the first semiconductor die 112 and the first tape102.

FIG. 4 shows a cross-sectional side view of a semiconductor device 400in accordance with a fourth embodiment of the present invention. Thefourth embodiment is similar to the third embodiment described above,except that the horizontally non-conductive layer 204 comprises ananisotropic conductive film that is conductive only in a verticaldirection by the air pressure in the vertical direction. In a preferredembodiment, the horizontally non-conductive layer 204 is disposedbetween the first tape 102 and the plurality of electrical contacts 114and electrically connects the plurality of bond pads 104 to theplurality of electrical contacts 114. In a preferred embodiment, theplurality of electrical contacts 114 are at least partially pressed intothe horizontally nonconductive layer 204 by air pressure, such that thehorizontally non-conductive layer 204 locks the plurality of electricalcontacts 114 in place to prevent shifting between the plurality ofelectrical contacts 114 and the plurality of bonding pads 104.

FIG. 5 shows a cross-sectional side view of a semiconductor device 500in accordance with a fifth embodiment of the present invention. Thefifth embodiment is similar to the third embodiment described above,except that the metal plate 202 is embedded within the second centerarea 118 of the second tape 116 and exposed from the second tape 116 toachieve better heat dissipation. FIG. 6 is a top plan view of the secondtape 116 and the metal plate 202 of FIG. 5 in accordance with the fifthembodiment of the present invention, which shows that the metal plate202 is embedded within the second center area 118 of the second tape 116and exposed from the second tape 116.

FIG. 7 is a top plan view of the first tape 102 of FIGS. 1-5 inaccordance with an embodiment of the present invention. The first tape102 includes a plurality of bonding pads 104 and a plurality ofconductive traces 106 formed thereon. The plurality of bonding pads 104are formed in a first center area 108 of the first tape 102, and theplurality of conductive traces 106 are formed in the first center area108 and extend from the plurality of bonding pads 104 to a firstperipheral area 110 that surrounds the first center area 108. In apreferred embodiment, the plurality of conductive traces 106 aregraphene traces.

FIG. 8 is a top plan view of the semiconductor device 100 in accordancewith an embodiment of the present invention. As shown in FIG. 8, thesemiconductor device 100 has a rectangular profile. FIG. 9 is a top planview of the semiconductor device 100 in accordance with anotherembodiment of the present invention. As shown in FIG. 9, thesemiconductor device 100 has a round profile.

FIG. 10 is a top plan view of a semiconductor device 600 in accordancewith yet another embodiment of the present invention. The embodimentshown in FIG. 10 is similar to the embodiment shown in FIG. 8 describedabove, except that there are multiple semiconductor dies 602-606attached to the first tape 102 and electrically connected to theconductive traces 106 formed on the first tape 102. In a preferredembodiment, the multiple semiconductor dies 602-606 includes functiondies such as a micro-controller unit, sensor dies, radio frequency (RF)dies, etc. The conductive traces 106 are preferably only provided forelectrically connecting the multiple semiconductor dies 602-606 and areentirely encapsulated by the first and second tapes 102 and 116 giventhat the semiconductor device 600 being a self-contained system. In apreferred embodiment, the semiconductor device 600 includes at least onepassive device 608 formed on the first tape 102. In another preferredembodiment, the semiconductor device 600 further includes at least onecoil 610, wherein the coil 610 is preferably formed by graphene traces.In a preferred embodiment, the multiple semiconductor dies 602-606, theat least one passive device 608 and the coil 610 are electricallyconnected to each other by way of the plurality of conductive traces 106to operate together as a system in the semiconductor device 600.

FIGS. 11-16 are a series of diagrams illustrating the steps inassembling or packaging a semiconductor device with the first tape 102that has a plurality of bonding pads 104 and a plurality of conductivetraces 106 formed thereon in accordance with an embodiment of thepresent invention. The plurality of bonding pads 104 are formed in afirst center area 108 of the first tape 102, and the plurality ofconductive traces 106 are formed in the first center area 108 and extendfrom the plurality of bonding pads 104 to a first peripheral area 110that surrounds the first center area 108.

Starting from FIG. 11, an array 700 of the first tapes 102 is provided.In a preferred embodiment, each first tape 102 has a plurality ofbonding pads 104 and a plurality of conductive traces 106 formedthereon. In a preferred embodiment, the array 700 of the first tapes 102is provided in a single piece of tape. In a preferred embodiment, theplurality of conductive traces 106 and the plurality of bonding pads 104comprises graphene.

In the next step illustrated in FIG. 12, a horizontally non-conductivelayer 204 is disposed over the first center area 108 of each of thefirst tape 102. In a preferred embodiment, the horizontallynon-conductive layer 204 comprises an anisotropic conductive film thatis conductive in a vertical direction when pressure is applied in thevertical direction. In a preferred embodiment, the horizontallynon-conductive layer 204 has a thickness ranging from 10 m to 50 m.

In the next step illustrated in FIG. 13, a first semiconductor die 112is mounted over the first center area 108 of each of the first tape 102and electrically connected to the plurality of bond pads 104 by way of aplurality of electrical contacts 114 and the horizontally non-conductivelayer 204 that is only conductive in the vertical direction toelectrically connect the plurality of bonding pads 104 to the pluralityof electrical contacts 114. In a preferred embodiment, a metal plate 202is further attached on a top surface of the first semiconductor die 112to protect the first semiconductor die 112 from being bent.

In the next step illustrated in FIGS. 14A and 14B, an array 800 ofsecond tapes 116 is provided. In a preferred embodiment, the array 800of the second tapes 116 is provided in a single piece of tape. Eachsecond tape 116 includes a second center area 118 and a secondperipheral area 120 surrounding the second center area 118. In apreferred embodiment, each second tape 116 further includes apre-half-cut portion 802 that is to be peeled off, as shown in the dotdash line in FIG. 14A. In a preferred embodiment, the pre-half-cutportion 802 is located at least one side of the second tape 116. Inanother preferred embodiment, as shown in FIG. 14B, the pre-half-cutportion 802 is formed in a ring shape along a peripheral edge of thesecond tape 116.

In the next step illustrated in FIG. 15A, the second tapes 116 areattached over corresponding first semiconductor dies 112. In a preferredembodiment, each the second tape 116 is attached to a correspondingmetal plates 202 that is attached on a top surface of the firstsemiconductor die 112. FIG. 15B is a cross-sectional side view of FIG.15A at line A-A, which shows that the second center area 118 of eachsecond tape 116 is attached over a corresponding first semiconductor die112, and the second peripheral area 120 of each second tape is attachedto the first peripheral area 110 of each first tape 102. In a preferredembodiment, the metal plate 202 is disposed between the firstsemiconductor die 112 and the second tape 116. In another preferredembodiment, the metal plate 202 is embedded within the second centerarea 118 of the second tape 116 and exposed from the second tape 116 toachieve better heat dissipation.

In the next step illustrated in FIG. 16A, a vacuum is applied betweenthe first and second tapes 102 and 116 to draw the first and secondtapes together, such that the first and second tapes 102 and 116encapsulate the first semiconductor die 112, the metal plate 202, theplurality of electrical contacts 114, and at least a part of theplurality of conductive traces 106. In a preferred embodiment, theplurality of electrical contacts 114 are at least partially pressed intothe horizontally non-conductive layer 204 by air pressure, such that thehorizontally non-conductive layer 204 locks the plurality of electricalcontacts 114 in place to prevent shifting between the plurality ofelectrical contacts 114 and the plurality of bonding pads 104. In apreferred embodiment, the first and second peripheral areas 110 and 120are attached to each other by way of adhesive materials disposedtherebetween. In another preferred embodiment, the first and secondperipheral areas 110 and 120 are heated and attached to each other. Anarray 900 of a plurality of semiconductor devices 200 is formed aftersaid encapsulation. Cutting is then performed along cutting lines 902 tosingulate the semiconductor devices 200 in the array from each other.FIG. 16B is a cross-sectional side view of FIG. 16A at line B-B, whichshows that a vacuum is applied between the first and second tapes 102and 116 to draw the first and second tapes together, such that the firstand second tapes 102 and 116 encapsulate the first semiconductor die112, the metal plate 202, the plurality of electrical contacts 114, andat least a part of the plurality of conductive traces 106. In apreferred embodiment, the horizontally non-conductive layer 204 is curedto lock the plurality of electrical contacts 114 in place, such thathorizontally non-conductive layer 204 prevents shifting between theplurality of electrical contacts 114 and the plurality of bond pads 104.The semiconductor device 200 is then singulated from the array bycutting long the cutting lines 902. The pre-half-cut portion 802 of thesecond tape 116 is peeled off to expose at least a portion of theconductive traces 106 to allow the exposed portion to act as an inputand output terminal of the semiconductor device 200 as shown in FIG. 17.In a preferred embodiment, said peeling off is performed before saidsingulation.

FIGS. 18-20 are a series of diagrams illustrating the steps inassembling or packaging a semiconductor device with the first tape 102that has a plurality of bonding pads 104 and a plurality of conductivetraces 106 formed thereon in accordance with another embodiment of thepresent invention. The plurality of bonding pads 104 are formed in afirst center area 108 of the first tape 102, and the plurality ofconductive traces 106 are formed in the first center area 108 and extendfrom the plurality of bonding pads 104 to a first peripheral area 110that surrounds the first center area 108.

As shown in FIG. 18, in a preferred embodiment, the horizontallynon-conductive layer 204 is provided with a plurality of openings 206.FIG. 19 shows a cross-sectional side view of the horizontallynon-conductive layer 204 that is attached to the first tape 102. Theplurality of openings 206 correspond to the plurality of bond pads 104,such that each of the plurality of bond pads 104 is exposed from thecorresponding openings 206. In a preferred embodiment, the horizontallynonconductive layer 204 comprises adhesive materials such as Bstageepoxy that is disposed on the first tape-102 by screen printing process.The B-stage epoxy comprises epoxy resin, polyimide, BismaleimideTriazine, etc.

In the next step illustrated in FIG. 20, the first semiconductor die 112is mounted to the first tape 102 and electrically connected to theplurality of bond pads 104 by way of a plurality of electrical contacts114, wherein the plurality of electrical contacts 114 are physically andelectrically connected to the plurality of bond pads 104 through theplurality of openings 206 in the horizontally non-conductive layer 204.The first semiconductor die 112, the plurality of electrical contacts114 and at least part of the conductive traces 106 are then encapsulatedby the first and second tapes 102 and 116 by a vacuum appliedtherebetween as discussed above.

The description of the preferred embodiments of the present inventionhas been presented for purposes of illustration and description, but isnot intended to be exhaustive or to limit the invention to the formsdisclosed. It will be appreciated by those skilled in the art thatchanges could be made to the embodiments described above withoutdeparting from the broad inventive concept thereof. It is understood,therefore, that this invention is not limited to the particularembodiment disclosed, but covers modifications within the spirit andscope of the present invention as defined by the appended claims.

What is claimed is:
 1. A method for assembling a semiconductor device,the method comprising: providing a first tape that has a plurality ofbonding pads and a plurality of conductive traces comprising grapheneformed thereon, wherein the plurality of bonding pads are formed in afirst center area of the first tape, and the plurality of conductivetraces are electrically connected to and extend from respective bottomsurfaces of the plurality of bonding pads to a first peripheral areasurrounding the first center area; attaching a first semiconductor dieto the first tape and electrically connecting the first die to theplurality of bond pads by way of a plurality of die electrical contacts;and attaching a second center area of a second tape to the firstsemiconductor die, and a second peripheral area surrounding the secondcenter area of the second tape to the first peripheral area of the firsttape by way of an adhesive therebetween, wherein the first and secondtapes encapsulate the first semiconductor die, the plurality of dieelectrical contacts, and at least a part of the plurality of conductivetraces.
 2. The method of claim 1, further comprising: attaching a metalplate on a top surface of the first semiconductor die, wherein the metalplate is disposed between the first semiconductor die and the secondtape.
 3. The method of claim 1, further comprising: attaching a metalplate on a top surface of the first semiconductor die, wherein the metalplate is embedded in the second tape.
 4. The method of claim 1, whereinthe second tape comprises a metal plate embedded in the second centerarea and attached to a top surface of the first semiconductor die. 5.The method of claim 1, further comprising: forming a horizontallynon-conductive layer at least partially over the first center area ofthe first tape; and curing the horizontally non-conductive layer,wherein the non-conductive layer locks the plurality of die electricalcontacts in place.
 6. The method of claim 5, wherein the horizontallynon-conductive layer comprises an anisotropic conductive layer that isconductive in a vertical direction and non- conductive in a horizontaldirection.
 7. The method of claim 6, wherein the horizontallynon-conductive layer is located between the first tape and the pluralityof die electrical contacts and electrically connects the plurality ofbond pads to the plurality of die electrical contacts.
 8. The method ofclaim 5, wherein the horizontally non-conductive layer comprises aplurality of openings corresponding to the plurality of bond pads,wherein the plurality of die electrical contacts are physically andelectrically connected to the plurality of bond pads through theplurality of openings.
 9. The method of claim 1, further comprisingapplying a vacuum between the first and second tapes to draw the firstand second tapes together.
 10. The method of claim 1, further comprisingpeeling off a part of the second tape to expose a portion of at leastone of the plurality of conductive traces to allow said exposed portionto act as an input and output terminal of the semiconductor device. 11.A method for assembling a semiconductor device, the method comprising:providing a first tape that has a plurality of bonding pads and aplurality of conductive traces formed thereon, wherein the plurality ofbonding pads and the plurality of conductive traces comprise graphene,wherein the plurality of bonding pads are formed in a first center areaof the first tape, and the plurality of conductive traces areelectrically connected to and extend from respective bottom surfaces ofthe plurality of bonding pads to a first peripheral area surrounding thefirst center area; attaching a first semiconductor die to the first tapeand electrically connecting the first die to the plurality of bond padsby way of a plurality of die electrical contacts; and attaching a secondcenter area of a second tape to the first semiconductor die, and asecond peripheral area surrounding the second center area of the secondtape to the first peripheral area of the first tape by way of anadhesive therebetween, wherein the first and second tapes encapsulatethe first semiconductor die, the plurality of die electrical contacts,and the plurality of conductive traces.
 12. The method of claim 11,further comprising: attaching a metal plate on a top surface of thefirst semiconductor die, wherein the metal plate is disposed between thefirst semiconductor die and the second tape.
 13. The method of claim 11,further comprising: attaching a metal plate on a top surface of thefirst semiconductor die, wherein the metal plate is embedded in thesecond tape.
 14. The method of claim 11, wherein the second tapecomprises a metal plate embedded in the second center area and attachedto a top surface of the first semiconductor die.
 15. The method of claim11, further comprising applying a vacuum between the first and secondtapes to draw the first and second tapes together.
 16. The method ofclaim 11, further comprising peeling off a part of the second tape toexpose a portion of at least one of the plurality of conductive tracesto allow said exposed portion to act as an input and output terminal ofthe semiconductor device.
 17. The method of claim 11, furthercomprising: forming a horizontally non-conductive layer at leastpartially over the first center area of the first tape; and curing thehorizontally non-conductive layer, wherein the non-conductive layerlocks the plurality of die electrical contacts in place.
 18. The methodof claim 17, wherein the horizontally non-conductive layer comprises aplurality of openings corresponding to the plurality of bond pads,wherein the plurality of die electrical contacts are physically andelectrically connected to the plurality of bond pads through theplurality of openings.
 19. The method of claim 17, wherein thehorizontally non-conductive layer comprises an anisotropic conductivelayer that is conductive in a vertical direction and non-conductive in ahorizontal direction.
 20. The method of claim 19, wherein thehorizontally non-conductive layer is located between the first tape andthe plurality of die electrical contacts and electrically connects theplurality of bond pads to the plurality of die electrical contacts.